Why did Zeus assume so many different forms for seduction?

Question

The character of Zeus is well-known for seducing many women, both human and goddesses. In many of these stories, Zeus assumes a form other than his true self.

The most famous is perhaps Leda - it is said that Zeus seduced her in the form of a swan (some versions specify that he came to her, in swan form, seeking protection from an eagle).

However, there are many other stories - this page lists several lovers who were not seduced in human form:

ANTIOPE: A Lady of Thebes in Boiotia (Central Greece) who was seduced by Zeus in the shape of a satyr. She bore him twin sons Amphion and Zethos which were exposed at birth.

DANAE: A Princess of Argos (in Central Greece) who was imprisoned by her father in a bronze tower. Zeus seduced her in the form of a golden shower, and she gave birth to a son, the hero Perseus.

EURYMEDOUSA: A Princess of Phthiotis (in Northern Greece) who was seduced by Zeus in the form of an ant. Their son was named Myrmidon (Ant-Man).

LEDA: A Queen of Lakedaimonia (in Southern Greece) who was seduced by Zeus in the form of a swan. She laid an egg from which were hatched the Dioskouroi twins

PHTHIA: A girl from Aegion in Akhaia (southern Greece). Zeus seduced her in the guise of a pigeon or dove.

In some stories, it makes complete sense why Zeus assumed the form he did:

ALKMENE: A Lady of Thebes in Boiotia (Central Greece) who was seduced by Zeus in the form of her own husband. She bore twins: Herakles by Zeus and Likymnios by her husband Amphitryon.

The story of Semele, Dionysus' mother, explains why Zeus does not present himself in his godly form - mortals perish when they look upon gods. However, it doesn't really explain why Zeus chose such varied, non-human, and frankly weird (ant?!), shapes for his seduction process. My question is, do any stories every offer an explanation for Zeus' shapes, or an indication of the motivation behind it?

Answer 1

I don't think it's explicitly said, but essentially, as being constantly unable to control himself, yet still being married to Hera, Zeus had two problems:

1. Hera, ever jealous was constantly after him. As a result, Zeus kept trying different tricks with which to hide from her (which never worked). Once, he tried blanketing the earth in clouds and transforming Io into a cow. From Ovid's Metamorphoses:

   Meanwhile Juno looked down into the heart of Argos, surprised that rapid mists had created night in shining daylight. She knew they were not vapours from the river, or breath from the damp earth. She looked around to see where her husband was, knowing by now the intrigues of a spouse so often caught in the act. When she could not find him in the skies, she said ‘Either I am wrong, or being wronged’ and gliding down from heaven’s peak, she stood on earth ordering the clouds to melt. Jupiter had a presage of his wife’s arrival and had changed Inachus’s daughter into a gleaming heifer. Even in that form she was beautiful. Saturnia approved the animal’s looks, though grudgingly, asking, then, whose she was, where from, what herd, as if she did not know. Jupiter, to stop all inquiry, lied, saying she had been born from the earth. Then Saturnia claimed her as a gift. What could he do? Cruel to sacrifice his love, but suspicious not to. Shame urges him to it, Amor urges not. Amor would have conquered Shame, but if he refused so slight a gift as a heifer to the companion of his race and bed, it might appear no heifer!

2. The women themselves were almost never interested, and so he transformed himself to make them more willing. This happened all the time; a good example was in the myth of Leda / Nemesis:

   But Zeus in the form of a swan consorted with Leda, and on the same night Tyndareus cohabited with her; and she bore Pollux and Helen to Zeus, and Castor and Clytaemnestra to Tyndareus. But some say that Helen was a daughter of Nemesis and Zeus; for that she, flying from the arms of Zeus, changed herself into a goose, but Zeus in his turn took the likeness of a swan and so enjoyed her; and as the fruit of their loves she laid an egg, and a certain shepherd found it in the groves and brought and gave it to Leda; and she put it in a chest and kept it; and when Helen was hatched in due time, Leda brought her up as her own daughter.

So, for one or the other of these reasons, Zeus pretty much had no choice, if he wanted to keep raping every beautiful woman he met. And he was the king of the gods, so he certainly wasn't going to give that up.

Answer 2

Presumably when people starting putting together all the local stories that would become "Greek myth" it turned out that Zeus had slept with a lot of women, in some rather odd guises. These may have made sense as part of some local cult, but as part of a human-shaped god's mythos they seem pretty weird.
Also, gods disguising themselves to rape a goddess or mortal woman wasn't limited to Zeus, although he used that trick a lot. (Poseidon, for example, disguised himself as a stallion after Demeter tried to hide from him by becoming a mare. Whether you see this as a rationalization of an older cult or a sneaky god trick is up to you.)
Zeus "seduced" his future wife, Hera, in the form of a bedraggled cuckoo, which she pitied and took to her breast, so he resumed his normal form and well... raped her.

Answer 3

Perhaps it was simply to trick the maidens.

It is well known that Hera is infuriated by Zeus's infidelity, and has a track record of taking out her wrath on the woman and even any children related to the affair, since she couldn't punish Zeus himself. She has gone all the way from permanent disfigurement (of various levels) to driving individuals to madness, and even murder. She's even tricked various mortals to kill someone they love.

Knowing Hera's fury, no matter how charming Zeus was, I imagine that many maidens were scared off by fear of her retaliation. Therefore when Zeus changed shapes to... whatever the maidens would not necessarily know was Zeus and be less wary of hooking up with him.